Conventionally, a gas meter device has been developed, which is capable of identifying an instrument which uses a gas in a fluid pipe system including the gas meter device. As such a gas meter device, for example, there is a gas meter device 100 disclosed in Patent Literature 1. A configuration of the gas meter device 100 will be described with reference to FIG. 21. FIG. 21 is a block diagram showing a schematic configuration of the gas meter device 100 according to a prior art.
As shown in FIG. 21, the gas meter device 100 includes a fluid passage 106 communicated with a home gas supply pipe (gas fluid passage 119). The gas meter device 100 further includes a memory 105, a gas shut-off valve 102, a flow measuring section 103, a calculating section 104, a comparator/determiner section 107, and a control circuit 116.
That is, in the gas meter device 100, the memory 105 preserves (contains) change determination values which are information as a criterion used to determine changes in gas use states of gas instruments 113 to 115.
The flow measuring section 103 measures a flow (flow rate) of the gas flowing through the fluid passage 106 at specified time intervals, and the calculating section 104 calculates a difference value of the measured flow value. Then, the comparator/determiner section 107 compares the difference value calculated by the calculating section 104 to the change determination values preserved in the memory 105 to determine the use state of any one of the gas instruments 113 to 115. The calculating section 104, the comparator/determiner section 107, and the gas shut-off valve 102 are controlled by the control circuit 116.
As described above, in the gas meter device 100, the calculating section 104 calculates the difference value of the instantaneous flow output from the flow measuring section 103 and determines the use state of any one of the gas instruments 113 to 115 based on a change amount of the difference value. The gas meter device 100 is configured to compare a change in the difference value of the measured gas flow to the change determination values preserved in the memory 105, to determine that the gas instrument using the gas is any one of the gas instruments 113 to 115.
As a gas meter device which determines the gas instrument using the gas, there is a gas meter device 200 disclosed in Patent Literature 2. A configuration of the gas meter device 200 disclosed in Patent Literature 2 will be described with reference to FIG. 22. FIG. 22 is a block diagram showing a schematic configuration of the gas meter device 200 according to a prior art.
As shown in FIG. 22, the gas meter device 200 includes a fluid passage 202 communicated with a gas pipe 216. The gas meter device 200 further includes a shut-off valve 222, a flow measuring section 204, a calculating section 208, a flow range division table preserving section 210, a difference value converting section 212, a code string generating section 214, an instrument determiner section 216, an instrument unique code string information preserving section 218, and an individual instrument flow calculating section 220. In the gas meter device 200, the calculating section 208 calculates a difference value at each specified time interval of the gas flow measured by the flow measuring section 204, and transmits the calculated difference value to the difference value converting section 212. Receiving the calculated difference value from the calculating section 208, the difference value converting section 212 converts the difference value at each specified time interval, into a code representing a specified flow range of divided flow ranges, with reference to a flow range division table 210a stored in the flow range division table preserving section 210. The code string generating section 214 generates a measurement code string which is the code string obtained by the difference value converting section 212. The measurement code string is change pattern information representing the change pattern of the flow of the fluid (gas) in a pseud manner. The instrument determiner section 216 compares the code string generated by the code string generating section 214 to instrument unique code strings unique to the instruments, which are stored in the instrument unique code string information preserving section 218, and determines that the gas instrument using the gas is any one of the gas instruments 213 to 215.
As described above, the gas meter device 200 disclosed in Patent Literature 2 is configured to determine the gas instrument using the gas, using an encoded value (code) derived by converting the difference value of the measured gas flow. This makes it possible to improve a calculation speed and an instrument determination accuracy while reducing a memory volume required for calculation performed when determining the gas instrument using the gas.    Patent Literature 1: Japanese Laid-Open Patent Application Publication No. 2006-313114    Patent Literature 2: Japanese Laid-Open Patent Application Publication No. 2008-309498